From some of the early MO:UL discussions, I recall that the vault was implemented as an Oracle database, possibly Oracle 9i or 10g. Finding "free" access to an Oracle installation doesn't seem likely, so I expect we'll need to migrate to some alternative RDBMS.

I think it's pretty safe to assume that the interface between the server application and the database is SQL, so it ought to be possible to use just about any database supporting SQL, such as PostgeSQL or mySQL, although I'd anticipate some performance issues might arise. There may also be some anomolies in the behaviour of some queries when applied to a non-Oracle DB. In my experience, mySQL is more prone to these kind of things than PostgreSQL - it probably comes down to the level of compliance with ANSI-SQL 92/99 that the respective DBs achieve.

Are there other DBMSs we could consider?

I also guess that an empty table set could be provided by Cyan as an SQL query, assuming that there's no specific DB creation tooling as part of the server software.

I would hope that like many systems, multiple RDBMS platforms would be supported. Large shards wanting the power of Oracle and willing to pay for it could still use that. Or MS SQL for people who like Microsoft (yes, many do in fact *like* Microsoft). Free shards might opt for MySQL, if possible. I use MySQL a lot and would love to see it supported.

I would prefer having the SQL scripts necessary to create the initial dataset than just the tables, but it's easy enough to work backward to it.

Obviously if someone does have Oracle available then that ought to be (mostly) a no brainer. I hadn't actually thought about it before, but I suppose there's Oracle XE avaiable free. Might be a "quick win" there.

I didn't intentionally omit MS SQL, just forgot about it , and I'm also a big MySQL user myself, but I am aware of some limitations when compared to PostgreSQL (I was actually at a conference in Estonia last month where this very subject was discussed at some length - I'm afraid I didn't actually pay too much attention to that one )

I'm not sure what you mean by "free" oracle.
Do you just need the Cd's or dvd-roms?
I know a guy who works for a cd/dvd manufacturing place who has Oracle as one of the Clients.
So there's extra disks sitting around his warehouse i bet.
Or do you mean an open-source oracle?